Asterisk and HIPATH 3800/HG1500

Hi,
I’m trying to configure asterisk–>HG1500–>Siemens HIPATH 3800.
communications between HIPATH and Asterisk work fine in both directions.
My
problem: calling from asterisk extension to external number (PSTN trunk
on HIPATH) --> Calls are redirected to receptionist !

Any suggestions ?